1. Field of the Invention
The present invention relates to a reinforcing woven fabric for use in fiber reinforced composite materials such as fiber reinforced plastics (hereinafter referred to as FRP), fiber reinforced carbons (hereinafter referred to as FRC) and fiber reinforced metals (hereinafter referred to as FRM), and to a preformed material which is an intermediate substrate for molding such composite materials, a fiber reinforced composite material molded with the preformed material and a beam molded with the preformed material.
2. Description of the Prior Art
Reinforcing filamentary yarns are often used as a formation of a woven fabric where a fiber reinforced composite material is molded. For example, such a reinforcing woven fabric for an FRP beam is disclosed in JP-B-SHO-62-23139. The reinforcing woven fabric is constituted by an ordinary biaxially woven fabric wherein the size and density of warps and wefts are both equal to each other and the warps and the wefts cross each other at a right angle. A plurality of the reinforcing woven fabrics are laminated such that the warps or the wefts of the reinforcing woven fabrics extend in the directions having angles of .+-.45.degree. relative to the longitudinal direction of the beam in the web portion of the beam (hereinafter, this laminated layer is called ".+-.45.degree. layer".). In the flange portion of the beam, some group of the end portions of the laminated reinforcing woven fabrics, and the other are separated in opposite directions to form the flange portion, and a single or a plurality of the reinforcing woven fabrics are laminated on the surface of the separated end portions such that the warps or the wefts of the single or the plurality of the reinforcing woven fabrics extend in the longitudinal direction of the beam (hereinafter, this laminated layer is called "0.degree. layer".). A reason why the web portion is constructed of .+-.45.degree. layer is that such a layer is effective to resist a shear stress generated in the beam. A reason why 0.degree. layer is provided in the flange portion is because the strength and rigidity in the longitudinal direction of the beam are insufficient if only .+-.45.degree. layer is provided.
In such a lamination structure, however, since a boundary is present between .+-.45.degree. layer and 0.degree. layer in the flange portion, there occurs a problem that the laminated layers are liable to delaminate at the boundary. Moreover, it is troublesome to provide the 0.degree. layer additionally.
U.S. Pat. No. 4,177,306 discloses a laminated sectional girder having a web and a flange wherein .+-.45.degree. layer in the web is molded with unidirectional prepregs and 0.degree. layer in the flange is formed by extending the unidirectional prepregs to the flange portion and interposing additional unidirectional prepregs between the extended unidirectional prepregs. However, this has the same problem as that on the beam disclosed in JP-B-SHO-62-23139.